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JP2002084595

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2002084595
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
drive apparatus for a speaker, and more particularly to a drive apparatus for a speaker with high
efficiency in converting an electric signal into a force for driving a diaphragm.
[0002]
2. Description of the Related Art FIG. 5 shows a conventional flat loudspeaker, in which (A) is a
plan view and (B) is a cross-sectional view taken along the line bb.
[0003]
As shown in FIGS. 5 (A) and 5 (B), the speaker 1 is a vibrating membrane on which a pole piece 2,
two permanent magnets m and m, two plates 3A and 3B and a voice coil 4 are formed. It consists
of five.
[0004]
The pole piece 2 has a T-shaped cross section having a support 2a at the center, and the
permanent magnets m, m are fixed on the bottom plate 2b.
Plates 3A and 3B are provided on the permanent magnets m and m.
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Gaps g1 and g2 having a predetermined gap size are formed in the opposing portions of the
support 2a and the plates 3A and 3B.
[0005]
The pole piece 2 and the plates 3A and 3B are formed of a magnetic material, and the first and
second magnetic paths 6A and 6B as shown in FIG. 5B are formed.
[0006]
A vibrating film 5 made of a resin material such as polyimide is fixed between the plate 3A and
the plate 3B.
The vibrating film 5 is formed with a voice coil 4 in which a copper foil or the like is spirally
formed. In the speaker 1, the copper foil wire of the voice coil 4 is disposed so as to be located
between the gaps g1 and g2.
[0007]
When an electrical signal is supplied to the voice coil 4, the copper foil has a driving force F
according to Fleming's left hand law between the magnetic flux density B between the gaps g1
and g2 and the current I of the electrical signal. Works. The driving force F is generated in the
direction (Z direction) orthogonal to the direction of the current I and the magnetic field, and the
vibrating film 5 is excited, so that the speaker 1 emits a sound.
[0008]
As shown in FIG. 5 (B), in the speaker 1, the upper surfaces of the plates 3A and 3B and the end
surfaces of the columns 2a located therebetween are almost flush with each other. It is set.
Therefore, strictly speaking, the voice coil 4 does not exist between the gaps g1 and g2, and the
voice coil 4 is excited by receiving the leakage flux of the gaps g1 and g2.
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[0009]
However, in general, the driving force F generated by Fleming's left-hand rule is represented by
the outer product (F = I × B) of the current I of the electric signal and the magnetic flux density
B, but the flux density of the leakage flux is Since the magnetic flux density between g2 is
smaller, the generated driving force F is also smaller. For this reason, in order to output a
constant sound volume, the current I of the electrical signal has to be set large, and the power
consumption becomes large. That is, the speaker 1 has a problem that the conversion efficiency
at the time of converting the electric signal into the driving force F is low.
[0010]
Generally, the leakage flux has low linearity with respect to the distance from the gaps g1 and g2.
For this reason, the current I flowing through the voice coil 4 intersects with the nonuniform
portion (leakage flux) of the magnetic flux distribution, and the driving force F generated differs
depending on the position of the voice coil 4. Therefore, the speaker 1 has a problem that the
vibrating film 5 is easily excited by the distorted driving force.
[0011]
The present invention is intended to solve the above-mentioned conventional problems, and it is
an object of the present invention to provide a speaker capable of increasing the conversion
efficiency when converting an electric signal to a driving force and reducing the distortion factor.
There is.
[0012]
According to the present invention, there is provided a vibrating membrane having a sound
generation function, a voice coil formed on the vibrating membrane and given an electrical
signal, and a magnetic path through which a magnetic flux generated by a magnet passes. In a
speaker comprising a yoke to be formed and a gap formed in the magnetic path and comprising a
magnetic circuit for applying a magnetic field to the voice coil, the arrangement direction of each
wire of the voice coil is the direction of the magnetic field in the gap , And are disposed with a
predetermined inclination angle.
[0013]
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In the arrangement of the diaphragm in the above speaker, for example, the diaphragm is
arranged to be inclined between one yoke and the other yoke opposed to each other with the gap
interposed therebetween.
[0014]
Furthermore, the one yoke and the other yoke face each other in the state of being displaced in
the height direction.
[0015]
In the present invention, since the voice coil can be disposed in the gap in the magnetic circuit, it
is possible to directly cross the optimum magnetic flux to the voice coil.
That is, since the leakage flux does not cross as in the prior art, the conversion efficiency of the
driving force can be enhanced.
Further, since the diaphragm can be excited while the voice coil is mainly located in the gap,
generation of distorted driving force can be prevented.
Further, since the magnetic flux density in the gap is substantially uniform, the driving force that
can be obtained by inclining the voice coil does not differ from the driving force in the case
where the voice coil is arranged horizontally in the gap.
Rather, since the number of voice coils that can be disposed in the gap can be increased, the
driving force that can be obtained when a constant current flows can be increased.
[0016]
Further, according to the present invention, there is provided a vibrating membrane having a
sound generating function, a voice coil spirally formed on the vibrating membrane, a magnet for
applying a magnetic field to the voice coil, and a part of a magnetic circuit for passing the
magnetic field. Between the first yoke forming the first yoke, the second yoke fixed to the
magnet, the first yoke and the second yoke, and the gap between the first yoke and the second
yoke And the voice coil is disposed in the gap, and the end of the vibrating membrane is fixed by
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being held between the first yoke and the third yoke. It is characterized by being.
[0017]
In the above configuration, the vibrating membrane can be fixed with a simple configuration.
In addition, since only the outer edge portion of the vibrating membrane needs to be fixed, the
entire vibrating membrane can be vibrated, and a reduction in sound pressure can be prevented.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below
with reference to the drawings.
[0019]
FIG. 1 is a perspective view showing a first embodiment of a speaker according to the present
invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, FIG. 3 shows a second
embodiment, FIG. 4 is a sectional view from the same direction, and FIG. 4 is a view partially
showing the appearance of a magnetic field in the second embodiment.
FIG. 4 shows the relationship between the central second yoke and only one of the first yokes.
[0020]
As shown in FIGS. 1 and 2, the speaker 10 shown in the first embodiment is provided with a first
yoke 11 having a U-shaped cross section extending in the Y direction. At the center of the first
yoke 11, a rectangular permanent magnet M extending in the Y direction is fixed. The permanent
magnet M in this embodiment is magnetically attached to the N pole on the Z1 side and the S
pole on the Z2 side. A plate-like second yoke 12 is fixed on the permanent magnet M. Further,
plate-shaped third yokes 13 and 14 are fixed to both end faces 11a and 11b of the first yoke. A
first gap G1 is formed between one side surface 12b of the second yoke 12 and the side surface
13b of the third yoke 13, and the other side surface 12c of the second yoke 12 and the third
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surface are formed. A second gap G2 is formed between the side face 14b of the yoke 14 and the
second side face 14b. That is, in the speaker 10, the first magnetic path 15 is formed in the path
of permanent magnet M → second yoke 12 → first gap G1 → third yoke 13 → first yoke 11 →
permanent magnet M A second magnetic path 16 is formed along a path of permanent magnet M
→ second yoke 12 → second gap G2 → third yoke 14 → first yoke 11 → permanent magnet M.
Thus, a magnetic circuit is configured by the permanent magnet M, the first yoke 11, the second
yoke 12 and the third yokes 13 and 14.
[0021]
The thickness dimensions of the second yoke 12 and the third yokes 13 and 14 in the height
direction are the same, and the heights of the respective yokes are the same. .
[0022]
Between one end face 11a and the other end face 11b of the first yoke 11, a sheet-like vibrating
film 17 made of a heat-resistant resin material such as a polyimide film is provided.
The vibrating film 17 has one end held between one end face 11a of the first yoke 11 and the
lower surface 13c of the third yoke 13, and the other end is the other end face 11b of the first
yoke 11 and the third And the lower surface 14c of the yoke 14 of FIG. The central region 17A of
the vibrating film 17 is opposed to the upper surface of the second yoke 12 with a gap larger
than the amplitude.
[0023]
Outside the central region 17A of the vibrating membrane 17, a voice coil C wound substantially
in a spiral along the central region 17A is formed. The voice coil C is formed by printing a
conductive wire such as a copper foil wire on the vibrating film 17 by a photo-etching means or
the like, and is formed so as to surround the central region 17A. Both sides in the X direction
sandwiching the central region 17A of the vibrating membrane 17 are inclined surfaces 17B and
17B inclined downward, and a part of the conducting wire of the voice coil C located on the
inclined surfaces 17B and 17B is the above The first gap G1 and the second gap G2 are disposed.
Then, the arrangement direction (T direction) of the wires of the voice coil C and the directions
X2 and X1 of the magnetic fields in the first and second gaps G1 and G2 intersect with each
other at a predetermined inclination angle θ1. There is.
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[0024]
In the first embodiment, the magnetic field is generated from the inner second yoke 12 in the
direction (X direction) of the outer third yokes 13 and 14, and the current flowing in the voice
coil C is the same. Direction perpendicular to the plane of the drawing. For this reason, it is
possible to simultaneously generate the driving force F according to Fleming's left hand law in
the same direction (Z direction) in the first gap G1 and the second gap G in each of the
conducting wires. Therefore, by giving an alternating current electrical signal to the voice coil C,
the vibrating membrane 17 can be excited in the Z direction, and sound can be emitted from the
vibrating membrane 17.
[0025]
Also, since only the outer edge portion of the vibrating membrane 17 is supported by each yoke,
the effective area of the vibrating membrane 17 which actually vibrates can be made large. For
this reason, it is possible to prevent a drop in sound pressure on the low frequency range side. In
addition, since the number of voice coils C (conductors) that can be disposed in the first and
second gaps G1 and G2 can be increased compared to when the vibrating film 17 is provided
horizontally, the unit The driving force F per current can be increased.
[0026]
Next, in the speaker 20 of the second embodiment shown in FIG. 3, the first yoke 21 and the
third yokes 23 and 24 are the same as in the first embodiment, but permanent magnets The
height h obtained by adding the second yoke 22 on M is set to be smaller than the height H of
the end faces 21a and 21b of the first yoke 21 in order to secure the amplitude of the diaphragm
27. It is done.
[0027]
In the speaker 20, the vibrating film 27 is formed between the end face 21a of the first yoke 21
and the third yoke 23, and between the end face 21b of the first yoke 21 and the third yoke 24.
Both ends are fixed, and the vibrating membrane 27 is formed in one plane without bending.
[0028]
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In the speaker 20, both end surfaces 22b and 22c of the second yoke 22 are N poles, and end
surfaces 23b and 24b of the third yokes 23 and 24 are S poles.
The end surfaces 22b and 22c of the second yoke 22 and the end surfaces 23b and 24b of the
third yokes 23 and 24 are respectively misaligned in the height direction (Z direction), and the
intervals between them are the first and the second, respectively. Two gaps G1 and G2 are used.
[0029]
As shown in FIG. 4, in the first gap G1, the magnetic field intersects the vibrating film 27, ie, the
direction in which the conductors of the voice coil C are aligned, with a substantially constant
inclination angle θ2 .
Therefore, as in the first embodiment, the vibrating film 27 can be excited in the Z direction
according to the electric signal.
[0030]
In the first and second embodiments, the magnetic field at the first gap G1 and the second gap
G2 is constant, and the voice coil C can be disposed in the gaps G1 and G2. A uniform magnetic
flux can be passed through the voice coil C. For this reason, it is possible to prevent the driving
force F generated in the voice coil C from being dispersed due to the difference in the position in
the gap. Therefore, it is possible to prevent the vibrating membrane from being excited by the
distorted driving force.
[0031]
Furthermore, in each of the first and second embodiments, each vibrating film 17, 27 can be
supported only by its outer edge, so that the vibrating film 17, 27 can be vibrated in the Z
direction. It is possible to prevent the sound pressure drop in the low range, and to fix the
vibrating membrane with a simple configuration.
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[0032]
According to the present invention described in detail above, the electric-acoustic conversion
efficiency of a speaker in which a voice coil is sometimes formed on a flat diaphragm is
enhanced, and a low distortion is achieved. be able to.
[0033]
Brief description of the drawings
[0034]
1 is a perspective view showing a first embodiment of a speaker according to the present
invention,
[0035]
2 II-II cross-sectional view of FIG.
[0036]
3 shows a second embodiment, a cross-sectional view from the same direction as FIG.
[0037]
4 is a view partially showing the state of the magnetic field in the second embodiment,
[0038]
5 shows a conventional speaker, (A) is a plan view, (B) is a cross-sectional view taken along the
line bb,
[0039]
Explanation of sign
[0040]
10, 20 Speaker 11, 21 First yoke 12, 22 Second yoke 13, 14, 23, 24 Third yoke 17, 27 Vibrating
film 17A Central region C Voice coil M Magnet G1 First gap G2 Second Gap F driving force
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